This invention relates to a fifth wheel support assembly and, more particularly, to a fifth wheel support for use on a plural wheel supported patient support.
In a hospital environment, it is oftentimes desired to provide a motorized driving of a patient support, namely, a bed, from one location to another. Since a patient support is usually supported on four castered wheels, a fifth drive wheel is usually provided to facilitate the aforesaid driving movement. The fifth drive wheel is generally provided at some location within a polygon defined by the regions whereat the four castered wheels engage a floor surface. In addition, the motor that effects the driving of the auxiliary fifth wheel is usually battery powered and a rechargeable battery is generally provided onboard the patient support to provide the power to the motor. In addition, there is generally provided an attendant controlled switch for activating and deactivating the motor. In some instances, the motor is a reversible motor and the switch is provided to accommodate a driving of the motor in opposite directions. However, the structure in known fifth wheel driving arrangements for deploying and retracting the fifth wheel is generally complicated, particularly in relation to the feature that causes the auxiliary fifth wheel to remain in engagement with the floor in instances where the region of contact of the auxiliary fifth wheel with the floor is oriented in a plane generally below the plane containing the regions whereat each of the remaining wheels of the patient support engage the floor.
Accordingly, it is an object of this invention to provide a fifth wheel support assembly which is configured to facilitate a movement of a fifth wheel to a retracted position oriented above the floor surface as well as a movement urged by a spring mechanism into engagement with the floor and with sufficient force to accommodate undulations in the floor surface and maintaining the requisite frictional contact with the floor to provide a continued and smooth driving of the patient support along the floor surface.
It is a further object of the invention to provide a fifth wheel support assembly as aforesaid which has a lost motion connection between the wheel support assembly and the bed frame for effecting a raising and lowering of the auxiliary fifth wheel so that the lost motion connection can accommodate undulations in the floor surface.
It is a further object of the invention to provide an inexpensive support structure, as aforesaid, which is easy to assemble, easy to service and durable in operation.
The objects and purposes of the invention are met by providing a fifth wheel support assembly having a frame with plural floor engaging wheels mounted thereon. A housing configured for movement relative to the frame is provided as is a spring mechanism oriented between the frame and the housing so as to continually urge the housing toward the floor. An auxiliary wheel is mounted for rotation on an axle secured to the housing, a peripheral surface of the wheel normally engaging the floor in response to the spring mechanism urging the housing toward the floor. A drive motor mechanism is provided and is fastened either to the frame or to the housing. The drive motor mechanism has an elongate driven member that is retractable and extendable. A distal end of the driven member is fastened to the other of the frame and the housing by a fastening mechanism. The fastening mechanism includes a pin. The elongate driven member has an elongate track thereon and which is movable therewith and which guidingly receives thereon the pin. The elongate track has a stop configured to engage the pin in response to the elongate driven member being retracted to effect a movement of the housing away from the floor against the urging of the spring mechanism and, consequently, to cause a corresponding movement of the peripheral surface of the auxiliary wheel away from the floor.